The posterior approach is done from the back of the patient. This approach can be just a fusion of the vertebral bones or it can include removal of the problem disc. If the disc is removed, it is replaced with a bone graft, or an interbody fusion device. The surgeon moves the spinal nerves to one side and inserts the bone graft or interbody device between the vertebral bodies. This is called a posterior lumbar interbody fusion.

With a posterior approach, an incision is made in the middle of the lower back over the area of the spine that is going to be fused. The muscles are moved to the side so that the surgeon can see the back surface of the vertebrae. Once the spine is visible, the lamina of the vertebra is removed to take pressure off the dura and nerve roots. This allows the surgeon to see areas of pressure on the nerve roots caused by bone spurs, a bulging disc, or thickening of the ligaments. The surgeon can remove or trim these structures to relieve the pressure on the nerves. Once the surgeon is satisfied that all pressure has been removed from the nerves, a fusion is performed. 

TLIF is an adaptation of a posterior lumbar interbody fusion. There are several potential advantages of TLIF over the standard posterior approach:

• The procedure can allow your doctor to fuse both the anterior and posterior portions of your spine through a single posterior surgical approach.
• TLIF increases the chance for a successful fusion due to the larger area for bone graft placement. Bone graft can be placed both in the area behind the vertebrae, to the side of the vertebrae, and in the disc space between the vertebrae.
• Because the approach to your disc space and spinal canal with TLIF is from your side, this allows your doctor to perform the operation with minimal stretching of your nerve roots. The exposure of your spinal canal is done from one side only.
• TLIF uses a special spacer called an interbody fusion device that is placed between your vertebrae to help restore the space between the vertebrae (the disc space). This can help reduce irritation and pressure on your nerve roots from bone spurs and thickened ligaments that can be a source of leg pain.

The surgeon may use some type of metal screws, plates, and rods to hold the vertebrae in place while the spine fusion heals. Designed to stabilize and hold the bones together while the fusion heals, these devices have greatly improved the success rate of fusion in the lower back.

A type of device, called an interbody fusion device or cage, can be used to perform a spinal fusion between two or more vertebrae. These implants are designed to spread the two vertebrae apart while the fusion heals.